Trackback, Pingback and Refback — The What and How

Bloggers should have heard about trackback, pingback or refback, but they are not well understood. If you use Gogle to find information about it, a lot of those web results are misleading. Not that they contain false information, but those pages often represent older specifications.

Trackback, pingback and refback are types of linkback. A linkback is a method for web authors and bloggers to obtain notifications when other bloggers link to one of their documents — and for the linking blogs to notify the linked blogs.

Basically, what they do is to let a blog notifies other blogs that it is linking to them. For the linked blogs, this allows them to track who is linking to them. As blogging is also communication tool, besides publishing, this feature lets bloggers establish a conversation with other bloggers beyond the comment form.

A blogger may extend a conversation to his/her blog and still the linked blogger will notice the conversation if s/he decides to click and check the linked blogs out — which s/he should.

A linked blog may choose to display the linking blogs in the comments area of the blog, hence producing a backlink to the originating blog too.

Trackbacks

A trackback is a mean to connect a post you made on your blog to a post on another blog. This keeps a link between both posts so people are able to refer back and forth between the documents.

This is like reciprocal linking, just that the linked page will display the link to the linking blog automatically in the comment area of the blog.

It used to be that a blogger has to enter the trackback link specific to the blog post in order for the linking blog software to send trackback ping to the destination. This is no longer necessary since Trackback specification version 1.1, which was released in October 2002.

Trackbacks is now capable of detecting specific tracback URL for a blog post automatically (called auto-discovery), but the destination blog should have support for that in each document. Each blog post has different trackback URL.

Pingbacks

Like trackbacks, pingbacks function the same but using an entirely different protocol. A pingback notifies the linked blog(s) that the originating blog is linking to it/them.

A pingback is essentially an XML-RPC request sent from one blog to another. Pingback is less prone to spam than trackback because when a blog receives a pingaback from another blog, it goes out and check the originating blog for the existence of a live incoming link.

That doesn’t mean it is impossible to send sping (spam ping) packet using pingback though because a forgery or page cloaking can be done on the fly.

Unlike trackback, pingback uses the blog’s XML-RPC URL to send pingback. This means it is the same every time.

Refbacks

Refback is rarely used, but for the sake of completeness, I’ll include it on this post.

A refeback also allows a blogger to keep track of who is linking to, or referring to their articles. Instead of using a new protocol, refback uses HTTP referrer header to discover incoming links.

Referrer header is automatic with compliant web browsers. If you are on page A, click on a link on that page, the browser will request that page and put the URI to page A in the Referrer header.

As refbacks rely on the Referrer header information, the linked blog will not receive information unless someone actually clicks on the link to go to the linked page.

The linked blog may go out and extract relevant information such as the title, meta information and link text on the linking blog and alternatively displays the link on the page.

A check is usually necessary before this is done to avoid displaying links to web-based email and other URLs that is not publicly accessible.

Trackbacks vs. Pingbacks

Although they are very similar, both trackback and pingback use entirely different protocols. You may send trackback pings by inserting a trackback link in the trackbacks area in your blog software.

Pingback is done automatically by the supported blog software. If you have a link to another blog, it will send the pingback to the linked blog if you enable that option in your blog.

Pingback has simpler autodiscovery feature than trackback.

With trackback, the linking blog has to download the linked page and check for the RDF section that contains auto-discovery information. On the other hand, pingback discovers the URL to send pingbacks to in the HTTP header (the X-Pingback header) and in the header section of a HTML document.

The latter appears as:

How to Use Trackbacks and Pingbacks with WordPress

You can specify the trackback link of the post you lik to in the Trackbacks section on the new post page. WordPress will automatically send trackback ping to the specified URL.

If you choose to enable trackbacks and pingbacks, WordPress will auto-discover and send pingbacks to all blogs that are mentioned in your blog post. You can toggle this option by going to Settings → Discussion.

The option is named: Attempt to notify any blogs linked to from the article (slows down posting.)

You need to do nothing else besides that. I recommend you enable this option to encourage participation. Trackbacks and pingbacks are direct ways to let people know about links. They are not only useful to extend conversation but also build your network.

Even though I chose not to enable comments, I still enable this option so other bloggers may still notify me about their linking blog pages and discuss posted topics.

The Challenge: Pingback and Tracback Spam

Software are available that try to forge pingback and trackback pings so the linked blog believes the issuing blog actually links to the blog.

Because most blogs display the title and linking page, blog spammers may benefit from the direct referral traffic and/or search engine juice. The latter is true if the blog enables dofollow for tracbacks.

Just because your blog uses nofollow for comments and trackbacks doesn’t mean you will not get trackback spams though because such software run automatically, it cost nothing to send pingbacka and trackbacks to as many blogs as possible.

Fortunately, blog plugin such as Akismet filters most of these spam into the moderation queue and let the bloggers decide if they want to approve or delete those spam. It isn’t perfect but at least in my experience, it catches most trackback spam.

Here are a list of WordPress plugins that can help you control trackback and comment spam:

Simple Trackback Validation. This plugin performs two checks to make sure a trackback is valid. First, it checks if the IP address of the trackback sender is equal to the IP address of the webserver the trackback URL is referring to. It also retrieves the page located at the URL included in the trackback to see if it links to your blog.

Simple Spam Filter. This plugin examines trackback data. If it contains 5 or more links, bbcode style links, or spam words, and if the comment is very similar to previous comments, it will filter out the tracback.

WP_PingPreserver. If you are annoyed with WordPress for losing pings because WordPress discards pings that come in too fast, this plugin can be of help.

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